The present invention relates to an ultrasonic apparatus which executes an in-phase cumulation with respect to a wave front of a reflected wave from a desired position for a group of received signals from an array of transducers and, more particularly, to an imaging apparatus for obtaining an ultrasonic echogram.
An apparatus which sequentially selects elements of a transducer array and executes an in-phase cumulation of the receiving signals of the selected elements so as to obtain an in-phase state with respect to a reflected wave from a desired position is widely used in place of an imaging apparatus which sequentially obtains ultrasonic echograms by mechanically scanning a single transducer having a high directivity. Further, the in-phase cumulation technique is also used in the field of flow rate detection using the Doppler shift and the field of ultrasonic detection in order to control a point response function, in other words, to form a receiving beam having desired spatial characteristics.
Generally, the received beam is formed by respectively leading reception signals from a plurality of transducer elements to an analog delay line and by adding the delayed signals. In an apparatus disclosed in U.S. Pat. No. 4,140,022, low frequency signals are produced by respectively mixing reference signals of the phases corresponding to the delays to be added to signals from the transducer elements, and the reception signals and the low frequency signals are respectively led to an analog delay line and are added.